3-2-1 backup rule

The 3-2-1 backup rule means keeping three copies of your data on two kinds of storage, with one copy stored offsite.

What it means for you

It helps reduce the risk of losing files to a failed drive, theft, fire or ransomware, and it is described in CISA data backup guidance. Time Machine on a Mac and Windows Backup are free starting points, and our guide shows how to add the offsite copy.

Guides on this topic

• Home Backups: the 3-2-1 Rule, Free Options First

  Back up photos and files with Time Machine or Windows Backup, add an offsite copy and keep one copy offline to help reduce ransomware risk.

• Local vs Cloud Storage for Security Cameras

  microSD, hubs, NVRs and cloud plans compared, and which to choose.

• Best PoE Camera and NVR Kits

  PoE and NVR explained, with kits for 24/7 whole-home recording to a local drive.

Related terms

• NAS
• Ransomware
• Phishing
• Password manager

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Definitions are short and general. For model-specific details, check your device maker’s own documentation.